(1) Field of the Invention
The present invention relates to a gas-tight article and a process for producing the same.
(2) Related Art Statement
It is known that a film of dense silicon carbide is effective as an oxidation resistive film to be formed on surfaces of ceramic members for use in high temperature atmosphere, such as liners for gas turbine parts and diesel engine parts. Further, it is known that surfaces of ceramic members are covered with thin films of dense silicon carbide in some uses such as a semiconductor-producing apparatus. In order to form such thin films, a chemical gas phase growing process, an electrochemical gas phase growing process, a sputtering process, a flame spraying process, etc. are known. For example, since a dense thin film having high purity and good quality can be formed by the gas phase process, this process is often used.
Gas-tight articles, which are to be exposed to a reactive plasma gas, are demanded, for example, in the production of semiconductors. As such a reactive plasma gas, CF.sub.4, NF.sub.3, ClF.sub.3, HF, HCl, HBr, etc. may be recited, which are all highly corrosive. Gas-tight articles, which can maintain gas-tightness over a prolonged period of time under an environment where they are exposed to such a highly corrosive gas, have been demanded.
The present inventors made investigations to cope with the demand, and encountered problems. That is, in order to enable gas-tight articles to be used in, for example, a semiconductor producing apparatus over a prolonged time period, the thickness of the film of silicon carbide must be increased. Recently, the area of the semiconductor wafer is increasing. Accordingly, in order to treat such a large size of the semiconductor wafer with for example low-pressure plasma, the large-area surface of the sintered body must be covered with a film of gas-tight silicon carbide.
However, since such a gas-tight article is to be actually subjected to heat impact between room temperature and high temperatures, the film of silicon carbide in the gas-tight article is likely to be cracked due to heat impact. If cracks are formed like this, the gas-tightness of the silicon carbide film is degraded to disable it to be used.